Interventions that incorporate a focus on social networks to change social norms are likely to result in sustained behavior change. One social network approach that has consistently demonstrated a 30% reduction in HIV risk behaviors is the Community Popular Opinion Leader (CPOL) approach, in which natural patterns of communication and influence are used to promote behavior change. A key to the success of social network interventions is identifying effective venues in which to intervene. Through this exploratory study we propose to identify venues where we can develop a CPOL intervention to reduce HIV, violence and substance use among young men. Our first aim is to identify and characterize venues where men, 15-19 years at high risk for HIV acquisition and transmission, socialize in Dar Es Salaam, Tanzania. To achieve Aim 1 we will apply the PLACE (Priorities for Local AIDS Control Efforts) methodology to identify and characterize venues where young men meet new sexual partners, and measure HIV risk, partner violence, and substance use among youth who socialize in these venues. Our second aim is to assess the feasibility and acceptability of a community popular-opinion leader intervention (CPOL) intervention targeting young men. To achieve Aim 2 we will conduct 60 in-depth interviews and 5 focus group discussions in venues identified through the PLACE assessment. We will describe attributes of male social networks that will influence the feasibility and acceptability of a CPOL intervention, and we will pilot aspects of the design and content of a CPOL intervention with young men. There are few interventions that have targeted changing young men's violence and HIV-related behaviors by influencing their social networks, and none, to our knowledge among young men in Africa. The findings will lay the groundwork for a trial to test the efficacy of a venue-based, popular-opinion leader intervention for young men. Youth in settings like Tanzania are disproportionately affected by the HIV epidemic. Strategies to engage young men in HIV prevention efforts are critically needed. This venue-based approach to HIV prevention with male social networks expands upon a successful social network approach to HIV prevention by incorporating a focus on other risk behaviors, namely partner violence and substance use.